Semi-solid electrodes having high rate capability

ABSTRACT

Embodiments described herein relate generally to electrochemical cells having high rate capability, and more particularly to devices, systems and methods of producing high capacity and high rate capability batteries having relatively thick semi-solid electrodes. In some embodiments, an electrochemical cell includes an anode, a semi-solid cathode that includes a suspension of an active material and a conductive material in a liquid electrolyte, and an ion permeable membrane disposed between the anode and the cathode. The semi-solid cathode has a thickness in the range of about 250 μm-2,500 μm, and the electrochemical cell has an area specific capacity of at least 5 mAh/cm 2  at a C-rate of C/2.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 61/736,798, filed Dec. 13, 2012, and U.S. ProvisionalApplication No. 61/787,382, filed Mar. 15, 2013, the disclosures of eachof which are hereby incorporated by reference in their entirety.

BACKGROUND

Embodiments described herein relate generally to electrochemical cellshaving high rate capability, and more particularly to devices, systemsand methods of producing high capacity and high rate capabilitybatteries having relatively thick semi-solid electrodes.

Batteries are typically constructed of solid electrodes, separators,electrolyte, and ancillary components such as, for example, packaging,thermal management, cell balancing, consolidation of electrical currentcarriers into terminals, and/or other such components. The electrodestypically include active materials, conductive materials, binders andother additives.

Some known methods for preparing batteries include coating a metallicsubstrate (e.g., a current collector) with slurry composed of an activematerial, a conductive additive, and a binding agent dissolved ordispersed in a solvent, evaporating the solvent, and calendering thedried solid matrix to a specified thickness. The electrodes are thencut, packaged with other components, infiltrated with electrolyte andthe entire package is then sealed.

Such known methods generally involve complicated and expensivemanufacturing steps such as casting the electrode and are only suitablefor electrodes of limited thickness, for example, less than 100 μm(final single sided coated thickness). These known methods for producingelectrodes of limited thickness result in batteries with lower capacity,lower energy density and a high ratio of inactive components to activematerials. Furthermore, the binders used in known electrode formulationscan increase tortuosity and decrease the ionic conductivity of theelectrode.

Thus, it is an enduring goal of energy storage systems development tosimplify and reduce manufacturing cost, reduce inactive components inthe electrodes and finished batteries, and increase energy density,charge capacity and overall performance.

SUMMARY

Embodiments described herein relate generally to electrochemical cellshaving high rate capability, and more particularly to devices, systemsand methods of producing high capacity and high rate capabilitybatteries having relatively thick semi-solid electrodes. In someembodiments, an electrochemical cell includes an anode, a semi-solidcathode that includes a suspension of an active material and aconductive material in a liquid electrolyte, and an ion permeablemembrane disposed between the anode and the cathode. The semi-solidcathode has a thickness in the range of about 250 μm-2,500 μm, and theelectrochemical cell has an area specific capacity of at least 5 mAh/cm²at a C-rate of C/2.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrochemical cell accordingto an embodiment.

FIG. 2 illustrates the areal discharge capacity vs. current density atvarious C-rates of four different semi-solid cathodes described herein,in comparison with commercially available batteries.

FIG. 3A-3B illustrate the capacity of an exemplary electrochemical cellas a function of charge and discharge rate, and a samplecharge/discharge curve.

DETAILED DESCRIPTION

Consumer electronic batteries have gradually increased in energy densitywith the progress of lithium-ion battery technology. The stored energyor charge capacity of a manufactured battery is a function of: (1) theinherent charge capacity of the active material (mAh/g), (2) the volumeof the electrodes (cm³) (i.e., the product of the electrode thickness,electrode area, and number of layers (stacks)), and (3) the loading ofactive material in the electrode media (e.g., grams of active materialper cm³ of electrode media). Therefore, to enhance commercial appeal(e.g., increased energy density and decreased cost), it is generallydesirable to increase the areal charge capacity (mAh/cm²). The arealcharge capacity can be increased, for example, by utilizing activematerials that have a higher inherent charge capacity, increasingrelative percentage of active charge storing material (i.e., “loading”)in the overall electrode formulation, and/or increasing the relativepercentage of electrode material used in any given battery form factor.Said another way, increasing the ratio of active charge storingcomponents (e.g., the electrodes) to inactive components (e.g., theseparators and current collectors), increases the overall energy densityof the battery by eliminating or reducing components that are notcontributing to the overall performance of the battery. One way toaccomplish increasing the areal charge capacity, and therefore reducingthe relative percentage of inactive components, is by increasing thethickness of the electrodes.

Conventional electrode compositions have capacities of approximately150-200 mAh/g and generally cannot be made thicker than about 100 μmbecause of certain performance and manufacturing limitations. Forexample, i) conventional electrodes having a thickness over 100 μm(single sided coated thickness) typically have significant reductions intheir rate capability due to diffusion limitations through the thicknessof the electrode (e.g. porosity, tortuosity, impedance, etc.) whichgrows rapidly with increasing thickness; ii) thick conventionalelectrodes are difficult to manufacture due to drying and postprocessing limitations, for example, solvent removal rate, capillaryforces during drying that leads to cracking of the electrode, pooradhesion of the electrode to the current collector leading todelamination (e.g., during the high speed roll-to-roll calenderingprocess used for manufacturing conventional electrodes), migration ofbinder during the solvent removal process and/or deformation during asubsequent compression process; iii) without being bound to anyparticular theory, the binders used in conventional electrodes mayobstruct the pore structure of the electrodes and increase theresistance to diffusion of ions by reducing the available volume ofpores and increasing tortuosity (i.e. effective path length) byoccupying a significant fraction of the space between the functionalcomponents of the electrodes (i.e. active and conductive components). Itis also known that binders used in conventional electrodes can at leastpartially coat the surface of the electrode active materials, whichslows down or completely blocks the flow of ions to the activematerials, thereby increasing tortuosity.

Furthermore, known conventional batteries either have high capacity orhigh rate capability, but not both. A battery having a first chargecapacity at first C-rate, for example, 0.5 C generally has a secondlower charge capacity when discharged at a second higher C-rate, forexample, 2 C. This is due to the higher energy loss that occurs inside aconventional battery due to the high internal resistance of conventionalelectrodes (e.g. solid electrodes with binders), and a drop in voltagethat causes the battery to reach the low-end voltage cut-off sooner. Athicker electrode generally has a higher internal resistance andtherefore a lower rate capability. For example, a lead acid battery doesnot perform well at 1 C C-rate. They are often rated at a 0.2 C C-rateand even at this low C-rate, they cannot attain 100% capacity. Incontrast, Ultracapcitors can be discharged at an extremely high C-rateand still maintain 100% capacity, however, they have a much lowercapacity then conventional batteries. Accordingly, a need exists forbatteries with thicker electrodes, but without the aforementionedlimitations. The resulting batteries with superior performancecharacteristics, for example, superior rate capability and chargecapacity, and also are simpler to manufacture.

Semi-solid electrodes described herein can be made: (i) thicker (e.g.,greater than 250 μm—up to 2,000 μm or even greater) due to the reducedtortuosity and higher electronic conductivity of the semi-solidelectrode, (ii) with higher loadings of active materials, and (iii) witha simplified manufacturing process utilizing less equipment. Theserelatively thick semi-solid electrodes decrease the volume, mass andcost contributions of inactive components with respect to activecomponents, thereby enhancing the commercial appeal of batteries madewith the semi-solid electrodes. In some embodiments, the semi-solidelectrodes described herein are binderless and/or do not use bindersthat are used in conventional battery manufacturing. Instead, the volumeof the electrode normally occupied by binders in conventionalelectrodes, is now occupied by: 1) electrolyte, which has the effect ofdecreasing tortuosity and increasing the total salt available for iondiffusion, thereby countering the salt depletion effects typical ofthick conventional electrodes when used at high rate, 2) activematerial, which has the effect of increasing the charge capacity of thebattery, or 3) conductive additive, which has the effect of increasingthe electronic conductivity of the electrode, thereby countering thehigh internal impedance of thick conventional electrodes. The reducedtortuosity and a higher electronic conductivity of the semi-solidelectrodes described herein, results in superior rate capability andcharge capacity of electrochemical cells formed from the semi-solidelectrodes. Since the semi-solid electrodes described herein, can bemade substantially thicker than conventional electrodes, the ratio ofactive materials (i.e., the semi-solid cathode and/or anode) to inactivematerials (i.e. the current collector and separator) can be much higherin a battery formed from electrochemical cell stacks that includesemi-solid electrodes relative to a similar battery formed formelectrochemical cell stacks that include conventional electrodes. Thissubstantially increases the overall charge capacity and energy densityof a battery that includes the semi-solid electrodes described herein.

In some embodiments, the electrode materials described herein can be aflowable semi-solid or condensed liquid composition. A flowablesemi-solid electrode can include a suspension of an electrochemicallyactive material (anodic or cathodic particles or particulates), andoptionally an electronically conductive material (e.g., carbon) in anon-aqueous liquid electrolyte. Said another way, the active electrodeparticles and conductive particles are co-suspended in an electrolyte toproduce a semi-solid electrode. Examples of battery architecturesutilizing semi-solid suspensions are described in International PatentPublication No. WO 2012/024499, entitled “Stationary, Fluid RedoxElectrode,” and International Patent Publication No. WO 2012/088442,entitled “Semi-Solid Filled Battery and Method of Manufacture,” theentire disclosures of which are hereby incorporated by reference.

In some embodiments, semi-solid electrode compositions (also referred toherein as “semi-solid suspension” and/or “slurry”) described herein canbe mixed in a batch process e.g., with a batch mixer that can include,e.g., a high shear mixture, a planetary mixture, a centrifugal planetarymixture, a sigma mixture, a CAM mixture, and/or a roller mixture, with aspecific spatial and/or temporal ordering of component addition, asdescribed in more detail herein. In some embodiments, slurry componentscan be mixed in a continuous process (e.g. in an extruder), with aspecific spatial and/or temporal ordering of component addition.

The mixing and forming of a semi-solid electrode generally includes: (i)raw material conveyance and/or feeding, (ii) mixing, (iii) mixed slurryconveyance, (iv) dispensing and/or extruding, and (v) forming. In someembodiments, multiple steps in the process can be performed at the sametime and/or with the same piece of equipment. For example, the mixingand conveyance of the slurry can be performed at the same time with anextruder. Each step in the process can include one or more possibleembodiments. For example, each step in the process can be performedmanually or by any of a variety of process equipment. Each step can alsoinclude one or more sub-processes and, optionally, an inspection step tomonitor process quality.

In some embodiments, the process conditions can be selected to produce aprepared slurry having a mixing index of at least about 0.80, at leastabout 0.90, at least about 0.95, or at least about 0.975. In someembodiments, the process conditions can be selected to produce aprepared slurry having an electronic conductivity of at least about 10⁻⁶S/cm, at least about 10⁻⁵ S/cm, at least about 10⁻⁴ S/cm, at least about10⁻³ S/cm, or at least about 10⁻² S/cm. In some embodiments, the processconditions can be selected to produce a prepared slurry having anapparent viscosity at room temperature of less than about 100,000 Pa-s,less than about 10,000 Pa-s, or less than about 1,000 Pa-s, all at anapparent shear rate of 1,000 s⁻¹. In some embodiments, the processconditions can be selected to produce a prepared slurry having two ormore properties as described herein. Examples of systems and methodsthat can be used for preparing the semi-solid compositions and/orelectrodes are described in U.S. Patent Application No. 13/832,861,filed Mar. 15, 2013, entitled “Electrochemical Slurry Compositions andMethods for Preparing the Same,” the entire disclosure of which ishereby incorporated by reference.

As used herein, the term “about” and “approximately” generally mean plusor minus 10% of the value stated, e.g., about 250 μm would include 225μm to 275 μm, about 1,000 μm would include 900 μm to 1,100 μm.

As used herein, the term “semi-solid” refers to a material that is amixture of liquid and solid phases, for example, such as particlesuspension, colloidal suspension, emulsion, gel, or micelle.

As used herein, the term “condensed ion-storing liquid” or “condensedliquid” refers to a liquid that is not merely a solvent, as in the caseof an aqueous flow cell semi-solid cathode or anode, but rather, it isitself redox active. Of course, such a liquid form may also be dilutedby or mixed with another, non-redox active liquid that is a diluent orsolvent, including mixing with such a diluent to form a lower-meltingliquid phase, emulsion or micelles including the ion-storing liquid.

As used herein, the terms “activated carbon network” and “networkedcarbon” relate to a general qualitative state of an electrode. Forexample, an electrode with an activated carbon network (or networkedcarbon) is such that the carbon particles within the electrode assume anindividual particle morphology and arrangement with respect to eachother that facilitates electrical contact and electrical conductivitybetween particles and through the thickness and length of the electrode.Conversely, the terms “unactivated carbon network” and “unnetworkedcarbon” relate to an electrode wherein the carbon particles either existas individual particle islands or multi-particle agglomerate islandsthat may not be sufficiently connected to provide adequate electricalconduction through the electrode.

In some embodiments, an electrochemical cell for storing energy includesan anode, a semi-solid cathode including a suspension of an activematerial and a conductive material in a non-aqueous liquid electrolyte,and an ion permeable separator disposed between the anode and thecathode. The semi-solid cathode can have a thickness in the range ofabout 250 μm to about 2,000 μm. In some embodiments, the electrochemicalcell is configured such that at a C-rate of C/4, the electrochemicalcell has an area specific discharge capacity (also referred to as “arealcapacity”) of at least 5 mAh/cm², at least about 6 mAh/cm², at leastabout 7 mAh/cm², at least about 8 mAh/cm², at least about 9 mAh/cm², orat least about 10 mAh/cm². In some embodiments, at a C-rate of C/2, theelectrochemical cell has an areal capacity of at least 5 mAh/cm², atleast about 6 mAh/cm², at least about 7 mAh/cm², at least about 8mAh/cm², or at least about 9 mAh/cm². In some embodiments, at a C-rateof 1 C, the electrochemical cell has an areal capacity of at least 4mAh/cm², at least about 5 mAh/cm², at least about 6 mAh/cm², or at leastabout 7 mAh/cm². In some embodiments, at a C-rate of 2 C, theelectrochemical cell has an areal capacity of at least 3 mAh/cm², atleast about 4 mAh/cm², or at least about 5 mAh/cm². In some embodiments,at C-rates between about 2 C and about 5 C, the electrochemical cell hasan areal capacity of at least about 1 mAh/cm², or at least about 2mAh/cm².

In some embodiments, the thickness of the semi-solid cathode is at leastabout 250 μm. In some embodiments, the thickness of the semi-solidelectrodes can be at least about 300 μm, at least about 350 μm, at leastabout 400 μm, at least about 450 μm, at least about 500 μm, at leastabout 600 μm, at least about 700 μm, at least about 800 μm, at leastabout 900 μm, at least about 1,000 μm, at least about 1,500 μm, and upto about 2,000 μm, inclusive of all thicknesses therebetween.

In some embodiments, the anode can be a conventional anode, for example,a lithium metal anode or a calendered anode. In some embodiments, theanode can be a semi-solid anode that can have a thickness that issubstantially similar to the thickness of the semi-solid cathode suchas, for example, of at least abut 250 μm, at least about 300 μm, atleast about 350 μm, at least about 400 μm, at least about 450 μm, atleast about 500 μm, and so on.

In some embodiments, the thickness of the semi-solid electrodes can bein the range of about 250 μm to about 2,000 μm, about 300 μm to about2,000 μm, about 350 μm to about 2,000 μm, 400 μm to about 2,000 μm,about 450 μm to about 2,000 μm, about 500 to about 2,000 μm, about 250μm to about 1,500 μm, about 300 μm to about 1,500 μm, about 350 μm toabout 1,500 μm, about 400 μm to about 1,500 μm, about 450 μm to about1,500 μm, about 500 to about 1,500 μm, about 250 μm to about 1,000 μm,about 300 μm to about 1,000 μm, about 350 μm to about 1,000 μm, about400 μm to about 1,000 μm, about 450 μm to about 1,000 μm, about 500 μmto about 1,000 μm, about 250 μm to about 750 μm, about 300 μm to about750 μm, about 350 μm to about 750 μm, about 400 μm to about 750 μm,about 450 μm to about 750 μm, about 500 μm to about 750 μm, about 250 μmto about 700 μm, about 300 μm to about 700 μm, about 350 μm to about 700μm, about 400 μm to about 700 μm, about 450 μm to about 700 μm, about500 μm to about 700 μm, about 250 μm to about 650 μm, about 300 μm toabout 650 μm, about 350 μm to about 650 μm, about 400 μm to about 650μm, about 450 μm to about 650 μm, about 500 μm to about 650 μm, about250 μm to about 600 μm, about 300 μm to about 600 μm, about 350 μm toabout 600 μm, about 400 μm to about 600 μm, about 450 μm to about 600μm, about 500 μm to about 600 μm, about 250 μm to about 550 μm, about300 μm to about 550 μm, about 350 μm to about 550 μm, about 400 μm toabout 550 μm, about 450 μm to about 550 μm, or about 500 μm to about 550μm, inclusive of all ranges or any other distance therebetween.

In some embodiments, a semi-solid anode can include an anode activematerial selected from lithium metal, carbon, lithium-intercalatedcarbon, lithium nitrides, lithium alloys and lithium alloy formingcompounds of silicon, bismuth, boron, gallium, indium, zinc, tin, tinoxide, antimony, aluminum, titanium oxide, molybdenum, germanium,manganese, niobium, vanadium, tantalum, gold, platinum, iron, copper,chromium, nickel, cobalt, zirconium, yttrium, molybdenum oxide,germanium oxide, silicon oxide, silicon carbide, any other materials oralloys thereof, and any other combination thereof.

In some embodiments, a semi-solid cathode can include about 20% to about75% by volume of an active material. In some embodiments, a semi-solidcathode can include about 40% to about 75% by volume, or 50% to about75% by volume of an active material.

In some embodiments, a semi-solid cathode can include about 0.5% toabout 25% by volume of a conductive material. In some embodiments, asemi-solid cathode can include about 1.0% to about 6% by volume of aconductive material.

In some embodiments, a semi-solid cathode can include about 25% to about70% by volume of an electrolyte. In some embodiments, a semi-solidcathode can include about 30% to about 50%, or about 20% to about 40% byvolume of an electrolyte.

In some embodiments, a semi-solid anode can include about 20% to about75% by volume of an active material. In some embodiments, a semi-solidanode can include about 40% to about 75% by volume, or 50% to about 75%by volume of an active material.

In some embodiments, a semi-solid anode can include about 0% to about10% by volume of a conductive material. In some embodiments, asemi-solid anode can include about 1% to about 6%, or about 0.5% toabout 2% by volume of a conductive material.

In some embodiments, a semi-solid anode can include about 10% to about70% by volume of an electrolyte. In some embodiments, a semi-solid anodecan include about 30% to about 50%, or about 20% to about 40% by volumeof an electrolyte.

In some embodiments, a semi-solid cathode or semi-solid anode caninclude less than about 10% by volume of a polymeric binder. In someembodiments, a semi-solid cathode or semi-solid anode can include lessthan about 5% by volume, or less than 3% by volume, or less than 1% byvolume of a polymeric binder. In some embodiments, the polymeric bindercomprises polyvinylidene difluoride (PVdF).

In some embodiments, an electrochemical cell includes a semi-solidcathode that can include about 60% to about 80% by weight of an activematerial, about 1% to about 6% by weight of a conductive material, andabout 20% to about 40% by weight of a non-aqueous liquid electrolyte.The semi-solid cathode can have a thickness in the range of about 250 μmto about 2,000 gm. The electrochemical cell also include a semi-solidanode that can include about 50% to about 75% by weight of an activematerial, about 0.5% to about 2% by weight of a conductive material, andabout 20% to about 40% by weight of a non-aqueous liquid electrolyte.The semi-solid anode can have a thickness in the range of about 250 μmto about 2,000 μm. The semi-solid anode and the semi-solid cathode areseparated by an ion permeable membrane disposed therebetween.

FIG. 1 shows a schematic illustration of an electrochemical cell 100.The electrochemical cell 100 includes a positive current collector 110,a negative current collector 120 and a separator 130 disposed betweenthe positive current collector 110 and the negative current collector120. The positive current collector 110 is spaced from the separator 130and at least partially defines a positive electroactive zone. Thenegative current collector 120 is spaced from the separator 130 and atleast partially defines a negative electroactive zone. A semi-solidcathode 140 is disposed in the positive electroactive zone and an anode150 (e.g., a semi-solid anode) is disposed in the negative electroactivezone.

The semi-solid cathode and/or anode can be disposed on a currentcollector, for example, coated, casted, drop coated, pressed, rollpressed, or deposited using any other suitable method. The semi-solidcathode can be disposed on positive current collector and the semi-solidanode is disposed on a negative current collector. For example thesemi-solid electrode can be coated, casted, calendered and/or pressed onthe current collector. The positive current collector 110 and thenegative current collector 120 can be any current collectors that areelectronically conductive and are electrochemically inactive under theoperation conditions of the cell. Typical current collectors for lithiumcells include copper, aluminum, or titanium for the negative currentcollector and aluminum for the positive current collector, in the formof sheets or mesh, or any combination thereof.

Current collector materials can be selected to be stable at theoperating potentials of the positive and negative electrodes of anelectrochemical cell 100. For example, in non-aqueous lithium systems,the positive current collector can include aluminum, or aluminum coatedwith conductive material that does not electrochemically dissolve atoperating potentials of 2.5-5.0V with respect to Li/Li³⁰. Such materialsinclude platinum, gold, nickel, conductive metal oxides such as vanadiumoxide, and carbon. The negative current collector can include copper orother metals that do not form alloys or intermetallic compounds withlithium, carbon, and/or coatings comprising such materials disposed onanother conductor.

The semi-solid cathode and the semi-solid electrode included in anelectrochemical cell can be separated by a separator. For example, theseparator 130 can be any conventional membrane that is capable of iontransport. In some embodiments, the separator 130 is a liquidimpermeable membrane that permits the transport of ions therethrough,namely a solid or gel ionic conductor. In some embodiments the separator130 is a porous polymer membrane infused with a liquid electrolyte thatallows for the shuttling of ions between the cathode 140 and anode 150electroactive materials, while preventing the transfer of electrons. Insome embodiments, the separator 130 is a microporous membrane thatprevents particles forming the positive and negative electrodecompositions from crossing the membrane. In some embodiments, theseparator 130 is a single or multilayer microporous separator,optionally with the ability to fuse or “shut down” above a certaintemperature so that it no longer transmits working ions, of the typeused in the lithium ion battery industry and well-known to those skilledin the art. In some embodiments, the membrane materials comprisepolyethyleneoxide (PEO) polymer in which a lithium salt is complexed toprovide lithium conductivity, or Nation™ membranes which are protonconductors. For example, PEO based electrolytes can be used as themembrane, which is pinhole-free and a solid ionic conductor, optionallystabilized with other membranes such as glass fiber separators assupporting layers. PEO can also be used as a slurry stabilizer,dispersant, etc. in the positive or negative redox compositions. PEO isstable in contact with typical alkyl carbonate-based electrolytes. Thiscan be especially useful in phosphate-based cell chemistries with cellpotential at the positive electrode that is less than about 3.6 V withrespect to Li metal. The operating temperature of the redox cell can beelevated as necessary to improve the ionic conductivity of the membrane.

The cathode 140 can be a semi-solid stationary cathode or a semi-solidflowable cathode, for example of the type used in redox flow cells. Thecathode 140 can include an active material such as a lithium bearingcompound as described in further detail below. The cathode 140 can alsoinclude a conductive material such as, for example, graphite, carbonpowder, pyrloytic carbon, carbon black, carbon fibers, carbonmicrofibers, carbon nanotubes (CNTs), single walled CNTs, multi walledCNTs, fullerene carbons including “bucky balls,” graphene sheets and/oraggregate of graphene sheets, any other conductive material, alloys orcombination thereof. The cathode 140 can also include a non-aqueousliquid electrolyte as described in further detail below.

In some embodiments, the anode 150 can be a semi-solid stationary anode.In some embodiments, the anode 150 can be a semi-solid flowable anode,for example, of the type used in redox flow cells.

The anode 150 can also include a carbonaceous material such as, forexample, graphite, carbon powder, pyrloytic carbon, carbon black, carbonfibers, carbon microfibers, carbon nanotubes (CNTs), single walled CNTs,multi walled CNTs, fullerene carbons including “bucky balls”, graphenesheets and/or aggregate of graphene sheets, any other carbonaceousmaterial or combination thereof. In some embodiments, the anode 150 canalso include a non-aqueous liquid electrolyte as described in furtherdetail herein.

In some embodiments, the cathode 140 and the anode 150 can includeactive materials and optionally conductive materials in particulate formsuspended in a non-aqueous liquid electrolyte. In some embodiments, thecathode 140 and/or anode 150 particles (e.g., cathodic or anodicparticles) can have an effective diameter of at least about 1 μm. Insome embodiments, the cathodic or anodic particles have an effectivediameter between about 1 μm and about 10 μm. In other embodiments, thecathodic or anodic particles have an effective diameter of at leastabout 10 μm or more. In some embodiments, the cathodic or anodicparticles have an effective diameter of at less than about 1 μm. Inother embodiments, the cathodic or anodic particles have an effectivediameter of at less than about 0.5 μm. In other embodiments, thecathodic or anodic particles have an effective diameter of at less thanabout 0.25 μm. In other embodiments, the cathodic or anodic particleshave an effective diameter of at less than about 0.1 μm. In otherembodiments, the cathodic or anodic particles have an effective diameterof at less than about 0.05 μm. In other embodiments, the cathodic oranodic particles have an effective diameter of at less than about 0.01μm.

In some embodiments, a redox mediator is used to improve the chargetransfer within the semi-solid suspension. In some embodiments, theredox mediator is based on Fe²⁺ or V²⁺, V³⁺, or V⁴⁺. In someembodiments, the redox mediator is ferrocene.

In some embodiments, the conductive particles have shapes, which mayinclude spheres, platelets, or rods to optimize solids packing fraction,increase the semi-solid's net electronic conductivity, and improverheological behavior of semi-solids. In some embodiments, low aspect orsubstantially equiaxed or spherical particles are used to improve theability of the semi-solid to flow under stress.

In some embodiments, the particles have a plurality of sizes so as toincrease packing fraction. In particular, the particle size distributioncan be bi-modal, in which the average particle size of the largerparticle mode is at least 5 times larger than average particle size ofthe smaller particle mode. In some embodiments, the mixture of large andsmall particles improves flow of the material during cell loading andincreases solid volume fraction and packing density in the loaded cell.

In some embodiments, the nature of cathode 140 and/or anode 150semi-solid suspension can be modified prior to and subsequent to fillingof the negative electroactive zone and the positive electroactive zoneof an electrochemical cell to facilitate flow during loading and packingdensity in the loaded cell.

In some embodiments, the particle suspension is initially stabilized byrepulsive interparticle steric forces that arise from surfactantmolecules. After the particle suspension is loaded into the positiveelectroactive zone and/or the negative electroactive zone, chemical orheat treatments can cause these surface molecules to collapse orevaporate and promote densification. In some embodiments, thesuspension's steric forces are modified intermittently during loading.

For example, the particle suspension can be initially stabilized byrepulsive interparticle electrostatic double layer forces to decreaseviscosity. The repulsive force reduces interparticle attraction andreduces agglomeration. After the particle suspension is loaded into thepositive electroactive zone and/or negative electroactive zone, thesurface of the particles can be further modified to reduce interparticlerepulsive forces and thereby promote particle attraction and packing Forexample, ionic solutions such as salt solutions can be added to thesuspension to reduce the repulsive forces and promote aggregation anddensification so as to produce increased solids fraction loading afterfilling of the electroactive zones. In some embodiments, salt is addedintermittently during suspension loading to increase density inincremental layers.

In some embodiments, the positive and/or negative electroactive zonesare loaded with a particle suspension that is stabilized by repulsiveforces between particles induced by an electrostatic double layer orshort-range steric forces due to added surfactants or dispersants.Following loading, the particle suspension is aggregated and densifiedby increasing the salt concentration of the suspension. In someembodiments, the salt that is added to is a salt of a working ion forthe battery (e.g., a lithium salt for a lithium ion battery) and uponbeing added, causes the liquid phase to become an ion-conductingelectrolyte (e.g., for a lithium rechargeable battery, may be one ormore alkyl carbonates, or one or more ionic liquids). Upon increasingthe salt concentration, the electrical double layer causing repulsionbetween the particles is “collapsed”, and attractive interactions causethe particle to floc, aggregate, consolidate, or otherwise densify. Thisallows the electrode of the battery to be formed from the suspensionwhile it has a low viscosity, for example, by pouring, injection, orpumping into the positive and/or negative electroactive zones that canform a net-shaped electrode, and then allows particles within thesuspension to be consolidated for improved electrical conduction, higherpacking density and longer shelf life.

In some embodiments, the cathode 140 and/or anode 150 semi-solidsuspension can initially be flowable, and can be caused to becomenon-flowable by “fixing”. In some embodiments, fixing can be performedby the action of photopolymerization. In some embodiments, fixing isperformed by action of electromagnetic radiation with wavelengths thatare transmitted by the unfilled positive and/or negative electroactivezones of the electrochemical cell 100 formed from a semi-solid cathodeand/or semi-solid anode. In some embodiments, one or more additives areadded to the semi-solid suspensions to facilitate fixing.

In some embodiments, the injectable and flowable cathode 140 and/oranode 150 semi-solid is caused to become non-flowable by “plasticizing”.In some embodiments, the rheological properties of the injectable andflowable semi-solid suspension are modified by the addition of athinner, a thickener, and/or a plasticizing agent. In some embodiments,these agents promote processability and help retain compositionaluniformity of the semi-solid under flowing conditions and positive andnegative electroactive zone filling operations. In some embodiments, oneor more additives are added to the flowable semi-solid suspension toadjust its flow properties to accommodate processing requirements.

Semi-Solid Composition

In some embodiments, the cathode 140 and in some embodiments, the anode150 semi-solid provide a means to produce a substance that functionscollectively as an ion-storage/ion-source, electron conductor, and ionicconductor in a single medium that acts as a working electrode.

The cathode 140 and/or anode 150 semi-solid ion-storing redoxcomposition as described herein can have, when taken in moles per liter(molarity), at least 10M concentration of redox species. In someembodiments, the cathode 140 and/or the anode 150 semi-solidsion-storing redox composition can have at least 12M, at least 15M, or atleast 20M. The electrochemically active material can be an ion storagematerial and or any other compound or ion complex that is capable ofundergoing Faradaic reaction in order to store energy. The electroactivematerial can also be a multiphase material including the above describedredox-active solid mixed with a non-redox-active phase, includingsolid-liquid suspensions, or liquid-liquid multiphase mixtures,including micelles or emulsions having a liquid ion-storage materialintimately mixed with a supporting liquid phase. Systems that utilizevarious working ions can include aqueous systems in which Li⁺, Na⁺, orother alkali ions are the working ions, even alkaline earth working ionssuch as Ca²⁺, Mg²⁺, or Al³⁺. In each of these instances, a negativeelectrode storage material and a positive electrode storage material maybe required, the negative electrode storing the working ion of interestat a lower absolute electrical potential than the positive electrode.The cell voltage can be determined approximately by the difference inion-storage potentials of the two ion-storage electrode materials.

Systems employing negative and/or positive ion-storage materials thatare insoluble storage hosts for working ions, meaning that saidmaterials can take up or release the working ion while all otherconstituents of the materials remain substantially insoluble in theelectrolyte, are particularly advantageous as the electrolyte does notbecome contaminated with electrochemical composition products. Inaddition, systems employing negative and/or positive lithium ion-storagematerials are particularly advantageous when using non-aqueouselectrochemical compositions.

In some embodiments, the semi-solid ion-storing redox compositionsinclude materials proven to work in conventional lithium-ion batteries.In some embodiments, the positive semi-solid electroactive materialcontains lithium positive electroactive materials and the lithiumcations are shuttled between the negative electrode and positiveelectrode, intercalating into solid, host particles suspended in aliquid electrolyte.

In some embodiments, at least one of the semi-solid cathode 140 and/oranode 150 includes a condensed ion-storing liquid of a redox-activecompound, which may be organic or inorganic, and includes but is notlimited to lithium metal, sodium metal, lithium-metal alloys, galliumand indium alloys with or without dissolved lithium, molten transitionmetal chlorides, thionyl chloride, and the like, or redox polymers andorganics that can be liquid under the operating conditions of thebattery. Such a liquid form may also be diluted by or mixed withanother, non-redox-active liquid that is a diluent or solvent, includingmixing with such diluents to form a lower-melting liquid phase. In someembodiments, the redox-active component can comprise, by mass, at least10% of the total mass of the electrolyte. In other embodiments, theredox-active component will comprise, by mass, between approximately 10%and 25% of the total mass of the electrolyte. In some embodiments, theredox-active component will comprise by mass, at least 25% or more ofthe total mass of the electrolyte.

In some embodiments, the redox-active electrode material, whether usedas a semi-solid or a condensed liquid format as defined above, comprisesan organic redox compound that stores the working ion of interest at apotential useful for either the positive or negative electrode of abattery. Such organic redox-active storage materials include “p”-dopedconductive polymers such as polyaniline or polyacetylene basedmaterials, polynitroxide or organic radical electrodes (such as thosedescribed in: H. Nishide et al., Electrochim. Acta, 50, 827-831, (2004),and K. Nakahara, et al., Chem. Phys. Lett., 359, 351-354 (2002)),carbonyl based organics, and oxocarbons and carboxylate, includingcompounds such as Li₂C₆O₆, Li₂C₈H₄O₄, and Li₂C₆H₄O₄ (see for example M.Armand et al., Nature Materials, DOI: 10.1038/nmat2372) and organosulfurcompounds.

In some embodiments, organic redox compounds that are electronicallyinsulating are used. In some instance, the redox compounds are in acondensed liquid phase such as liquid or flowable polymers that areelectronically insulating. In such cases, the redox active slurry may ormay not contain an additional carrier liquid. Additives can be combinedwith the condensed phase liquid redox compound to increase electronicconductivity. In some embodiments, such electronically insulatingorganic redox compounds are rendered electrochemically active by mixingor blending with particulates of an electronically conductive material,such as solid inorganic conductive materials including but not limitedto metals, metal carbides, metal nitrides, metal oxides, and allotropesof carbon including carbon black, graphitic carbon, carbon fibers,carbon microfibers, vapor-grown carbon fibers (VGCF), fullerenic carbonsincluding “buckyballs”, carbon nanotubes (CNTs), multiwall carbonnanotubes (MWNTs), single wall carbon nanotubes (SWNTs), graphene sheetsor aggregates of graphene sheets, and materials comprising fullerenicfragments.

In some embodiments, such electronically insulating organic redoxcompounds are rendered electronically active by mixing or blending withan electronically conductive polymer, including but not limited topolyaniline or polyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes. The conductive additives form anelectrically conducting framework within the insulating liquid redoxcompounds that significantly increases the electrically conductivity ofthe composition. In some embodiments, the conductive addition forms apercolative pathway to the current collector. In some embodiments theredox-active electrode material comprises a sol or gel, including forexample metal oxide sols or gels produced by the hydrolysis of metalalkoxides, amongst other methods generally known as “sol-gelprocessing.” Vanadium oxide gels of composition V_(x)O_(y) are amongstsuch redox-active sol-gel materials.

Other suitable positive active materials for use in the cathode 140include solid compounds known to those skilled in the art as those usedin NiMH (Nickel-Metal Hydride) Nickel Cadmium (NiCd) batteries. Stillother positive electrode compounds for Li storage include those used incarbon monofluoride batteries, generally referred to as CFx, or metalfluoride compounds having approximate stoichiometry MF₂ or MF₃ where Mcomprises, for example, Fe, Bi, Ni, Co, Ti, or V. Examples include thosedescribed in H. Li, P. Balaya, and J. Maier, Li-Storage viaHeterogeneous Reaction in Selected Binary Metal Fluorides and Oxides,Journal of The Electrochemical Society, 151 [11] A1878-A1885 (2004), M.Bervas, A. N. Mansour, W.-S. Woon, J. F. Al-Sharab, F. Badway, F.Cosandey, L. C. Klein, and G. G. Amatucci, “Investigation of theLithiation and Delithiation Conversion Mechanisms in a Bismuth FluorideNanocomposites”, J. Electrochem. Soc., 153, A799 (2006), and I. Plitz,F. Badway, J. Al-Sharab, A. DuPasquier, F. Cosandey and G.G. Amatucci,“Structure and Electrochemistry of Carbon-Metal Fluoride NanocompositesFabricated by a Solid State Redox Conversion Reaction”, J. Electrochem.Soc., 152, A307 (2005).

As another example, fullerenic carbon including single-wall carbonnanotubes (SWNTs), multiwall carbon nanotubes (MWNTs), or metal ormetalloid nanowires may be used as ion-storage materials. One example isthe silicon nanowires used as a high energy density storage material ina report by C. K. Chan, H. Peng, G. Liu, K. Mcllwrath, X. F. Zhang, R.A. Huggins, and Y. Cui, High-performance lithium battery anodes usingsilicon nanowires, Nature Nanotechnology, published online 16 Dec. 2007;doi:10.1038/nnano.2007.411. In some embodiments, electroactive materialsfor the cathode 140 in a lithium system can include the general familyof ordered rocksalt compounds LiMO₂ including those having the α-NaFeO₂(so-called “layered compounds”) or orthorhombic-LiMnO₂ structure type ortheir derivatives of different crystal symmetry, atomic ordering, orpartial substitution for the metals or oxygen. M comprises at least onefirst-row transition metal but may include non-transition metalsincluding but not limited to Al, Ca, Mg, or Zr. Examples of suchcompounds include LiCoO₂, LiCoO₂ doped with Mg, LiNiO₂, Li(Ni, Co, Al)O₂(known as “NCA”) and Li(Ni, Mn, Co)O₂ (known as “NMC”). Other familiesof exemplary cathode 140 electroactive materials includes those ofspinel structure, such as LiMn₂O₄ and its derivatives, so-called“layered-spinel nanocomposites” in which the structure includesnanoscopic regions having ordered rocksalt and spinel ordering, olivinesLiMPO₄ and their derivatives, in which M comprises one or more of Mn,Fe, Co, or Ni, partially fluorinated compounds such as LiVPO₄F, other“polyanion” compounds as described below, and vanadium oxides V_(x)O_(y)including V₂O₅ and V₆O₁₁.

In some embodiments, the cathode 140 electroactive material comprises atransition metal polyanion compound, for example as described in U.S.Pat. No. 7,338,734. In some embodiments the active material comprises analkali metal transition metal oxide or phosphate, and for example, thecompound has a composition A_(x)(M′_(1-a)Ar_(a))_(y)(XD₄)_(z),A_(x)(M′_(1-a)Ar_(a))_(y)(DXD₄)_(z), orA_(x)(M′_(1-a)M″_(a))_(y)(X₂D₇)_(z), and have values such that x, plusy(1-a) times a formal valence or valences of M′, plus ya times a formalvalence or valence of M″, is equal to z times a formal valence of theXD₄, X₂D₇, or DXD₄ group; or a compound comprising a composition(A_(1-a)M″_(a))_(x)M′_(y)(XD₄)_(z),(A_(1-a)M″_(a))_(x)(M′_(y)(DXD₄)z(A_(1-a)M″_(a))_(x)M′_(y)(X₂D₇)_(z) andhave values such that (1-a)x plus the quantity ax times the formalvalence or valences of M″ plus y times the formal valence or valences ofM′ is equal to z times the formal valence of the XD₄, X₂D₇ or DXD₄group. In the compound, A is at least one of an alkali metal andhydrogen, M′ is a first-row transition metal, X is at least one ofphosphorus, sulfur, arsenic, molybdenum, and tungsten, M″ any of a GroupIIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIBmetal, D is at least one of oxygen, nitrogen, carbon, or a halogen. Thepositive electroactive material can be an olivine structure compoundLiMPO₄, where M is one or more of V, Cr, Mn, Fe, Co, and Ni, in whichthe compound is optionally doped at the Li, M or O-sites. Deficienciesat the Li-site are compensated by the addition of a metal or metalloid,and deficiencies at the 0-site are compensated by the addition of ahalogen. In some embodiments, the positive active material comprises athermally stable, transition-metal-doped lithium transition metalphosphate having the olivine structure and having the formula(Li_(1-x)Z_(x))MPO₄, where M is one or more of V, Cr, Mn, Fe, Co, andNi, and Z is a non-alkali metal dopant such as one or more of Ti, Zr,Nb, Al, or Mg, and x ranges from 0.005 to 0.05.

In other embodiments, the lithium transition metal phosphate materialhas an overall composition of Li_(1-x-z)M_(1+z)PO₄, where M comprises atleast one first row transition metal selected from the group consistingof Ti, V, Cr, Mn, Fe, Co and Ni, where x is from 0 to 1 and z can bepositive or negative. M includes Fe, z is between about 0.15-0.15. Thematerial can exhibit a solid solution over a composition range of0<x<0.15, or the material can exhibit a stable solid solution over acomposition range of x between 0 and at least about 0.05, or thematerial can exhibit a stable solid solution over a composition range ofx between 0 and at least about 0.07 at room temperature (22-25° C.). Thematerial may also exhibit a solid solution in the lithium-poor regime,e.g., where x≧0.8, or x≧0.9, or x≧0.95.

In some embodiments the redox-active electrode material comprises ametal salt that stores an alkali ion by undergoing a displacement orconversion reaction. Examples of such compounds include metal oxidessuch as CoO, Co₃O₄, NiO, CuO, MnO, typically used as a negativeelectrode in a lithium battery, which upon reaction with Li undergo adisplacement or conversion reaction to form a mixture of Li₂O and themetal constituent in the form of a more reduced oxide or the metallicform. Other examples include metal fluorides such as CuF₂, FeF₂, FeF₃,BiF₃, CoF₂, and NiF₂, which undergo a displacement or conversionreaction to form LiF and the reduced metal constituent. Such fluoridesmay be used as the positive electrode in a lithium battery. In otherembodiments the redox-active electrode material comprises carbonmonofluoride or its derivatives. In some embodiments the materialundergoing displacement or conversion reaction is in the form ofparticulates having on average dimensions of 100 nanometers or less. Insome embodiments the material undergoing displacement or conversionreaction comprises a nanocomposite of the active material mixed with aninactive host, including but not limited to conductive and relativelyductile compounds such as carbon, or a metal, or a metal sulfide. FeS₂and FeF₃ can also be used as cheap and electronically conductive activematerials in a nonaqueous or aqueous lithium system.

In some embodiments, the working ion is selected from the groupconsisting of Li⁺, Na⁺, H⁺, Mg²⁺, Al³⁺, or Ca²⁺.

In some embodiments, the working ion is selected from the groupconsisting of Li⁺ or Na⁺.

In some embodiments, the semi-solid ion-storing redox compositionincludes a solid including an ion-storage compound.

In some embodiments, the ion is proton or hydroxyl ion and the ionstorage compound includes those used in a nickel-cadmium or nickel metalhydride battery.

In some embodiments, the ion is lithium and the ion storage compound isselected from the group consisting of metal fluorides such as CuF₂,FeF₂, FeF₃, BiF₃, CoF₂, and NiF₂.

In some embodiments, the ion is lithium and the ion storage compound isselected from the group consisting of metal oxides such as CoO, Co₃O₄,NiO, CuO, MnO.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from compounds with formula(Li_(1-x)Z_(x))MPO₄, where M is one or more of V, Cr, Mn, Fe, Co, andNi, and Z is a non-alkali metal dopant such as one or more of Ti, Zr,Nb, Al, or Mg, and x ranges from 0.005 to 0.05.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from compounds with formulaLiMPO₄, where M is one or more of V, Cr, Mn, Fe, Co, and Ni, in whichthe compound is optionally doped at the Li, M or O-sites.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofA_(x)(M′_(1-a)M″_(a))_(y)(XD₄)_(z), A_(x)(M′_(1-a)M″_(a))_(y)(DXD₄)_(z),and A_(x)(M′_(1-a)M″_(a))_(y)(X₂D₇)_(z), wherein x, plus y(1-a) times aformal valence or valences of M′, plus ya times a formal valence orvalence of M″, is equal to z times a formal valence of the XD₄, X₂D₇, orDXD₄ group; and A is at least one of an alkali metal and hydrogen, M′ isa first-row transition metal, X is at least one of phosphorus, sulfur,arsenic, molybdenum, and tungsten, M″ any of a Group IIA, IIIA, IVA, VA,VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at leastone of oxygen, nitrogen, carbon, or a halogen.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofA_(1-a)M″_(a))_(x)M′_(y)(XD₄)_(z), (A_(1-a)M″_(a))_(x)M′_(y)(DXD₄)z andA_(1-a)M″_(a))_(x)M′_(y)(X₂D₇)_(z) where (1-a)x plus the quantity axtimes the formal valence or valences of M″ plus y times the formalvalence or valences of M′ is equal to z times the formal valence of theXD₄, X₂D₇ or DXD₄ group, and A is at least one of an alkali metal andhydrogen, M′ is a first-row transition metal, X is at least one ofphosphorus, sulfur, arsenic, molybdenum, and tungsten, M″ any of a GroupIIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIBmetal, D is at least one of oxygen, nitrogen, carbon, or a halogen.

In some embodiments, the ion is lithium and the ion storage compoundincludes an intercalation compound selected from the group consisting ofordered rocksalt compounds LiMO₂ including those having the includingthose having the α-NaFeO₂ and orthorhombic—LiMnO₂ structure type ortheir derivatives of different crystal symmetry, atomic ordering, orpartial substitution for the metals or oxygen, where M includes at leastone first-row transition metal but may include non-transition metalsincluding but not limited to Al, Ca, Mg or Zr.

In some embodiments, the semi-solid ion storing redox compositionincludes a solid including amorphous carbon, disordered carbon,graphitic carbon, or a metal-coated or metal decorated carbon.

In some embodiments, the semi-solid ion storing redox composition caninclude a solid including nanostructures, for example, nanowires,nanorods, and nanotetrapods.

In some embodiments, the semi-solid ion storing redox compositionincludes a solid including an organic redox compound.

In some embodiments, the positive electrode can include a semi-solid ionstoring redox composition including a solid selected from the groupsconsisting of ordered rocksalt compounds LiMO₂ including those havingthe α-NaFeO₂ and orthorhombic-LiMnO₂ structure type or their derivativesof different crystal symmetry, atomic ordering, or partial substitutionfor the metals or oxygen, wherein M Includes at least one first-rowtransition metal but may include non-transition metals including but notlimited to Al, Ca, Mg, or Zr. The negative electrode can includes asemi-solid ion-storing composition including a solid selected from thegroup consisting of amorphous carbon, disordered carbon, graphiticcarbon, or a metal-coated or metal-decorated carbon.

In some embodiments, the positive electrode can include a semi-solidion-storing redox composition including a solid selected from the groupconsisting of A_(x)(M′_(1-a)M″_(a))_(y)(XD₄)_(z),A_(x)(M′_(1-a)M″_(a))_(y)(DXD₄)_(z), andA_(x)(M′_(1-a)M″_(a))_(y)(X₂D₇)_(z), and where x, plus y(1-a) times aformal valence or valences of M′, plus ya times a formal valence orvalence of M″, is equal to z times a formal valence of the XD₄, X₂D₇, orDXD₄ group, and A is at least one of an alkali metal and hydrogen, M′ isa first-row transition metal, X is at least one of phosphorus, sulfur,arsenic, molybdenum, and tungsten, M″ any of a Group IIA, IIIA, IVA, VA,VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at leastone of oxygen, nitrogen, carbon, or a halogen and the negative electrodeincludes a semi-solid ion-storing redox composition including a solidselected from the group consisting of amorphous carbon, disorderedcarbon, graphitic carbon, or a metal-coated or metal-decorated carbon.

In some embodiments, the anode can include a semi-solid ion-storingredox composition including a compound with a spinel structure.

In some embodiments, the positive electrode includes a semi-solidion-storing redox composition including a compound selected from thegroup consisting of LiMn₂O₄ and its derivatives; layered-spinelnanocomposites in which the structure includes nanoscopic regions havingordered rocksalt and spinel ordering; so-called “high voltage spinels”with a potential vs. Li/Li+ that exceeds 4.3V including but not limitedto LiNi_(0.5)Mn_(1.5)O₄; olivines LiMPO₄ and their derivatives, in whichM includes one or more of Mn, Fe, Co, or Ni, partially fluorinatedcompounds such as LiVPO₄F, other “polyanion” compounds, and vanadiumoxides V_(x)O_(y) including V₂O₅ and V₆O₁₁.

In some embodiments the semi-solid battery is a lithium battery, and theanode 150 compound comprises graphite, graphitic or non-graphiticcarbon, amorphous carbon, mesocarbon microbeads, boron-carbon alloys,hard or disordered carbon, lithium titanate spinel, or a solid metal ormetal alloy or metalloid or metalloid alloy that reacts with lithium toform intermetallic compounds, e.g., Si, Ge, Sn, Bi, Zn, Ag, Al, anyother suitable metal alloy, metalloid alloy or combination thereof, or alithiated metal or metal alloy including such compounds as LiAl, Li₉Al₄,Li₃Al, LiZn, LiAg, Li₁₀Ag₃, Li₅B₄, Li₇B₆, Li₁₂Si₇, Li₂₁Si₈, Li₁₃Si₄,Li₂₁Si₅, Li₅Sn₂, Li₁₃Sn₅, Li₇Sn₂, Li₂₂Sn₅, Li₂Sb, Li₃Sb, LiBi, or Li₃Bi,or amorphous metal alloys of lithiated or non-lithiated compositions,any other materials or alloys thereof, or any other combination thereof.

In some embodiments, the electrochemical function of the semi-solidredox cell is improved by mixing or blending the cathode 140 and/oranode 150 particles with particulates of an electronically conductivematerial, such as solid inorganic conductive materials including but notlimited to metals, metal carbides, metal nitrides, metal oxides, andallotropes of carbon including carbon black, graphitic carbon, carbonfibers, carbon microfibers, vapor-grown carbon fibers (VGCF), fullereniccarbons including “buckyballs”, carbon nanotubes (CNTs), multiwallcarbon nanotubes (MWNTs), single wall carbon nanotubes (SWNTs), graphenesheets or aggregates of graphene sheets, and materials comprisingfullerenic fragments. In some embodiments, such electronicallyinsulating organic redox compounds are rendered electronically active bymixing or blending with an electronically conductive polymer, includingbut not limited to polyaniline or polyacetylene based conductivepolymers or poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole,polythiophene, poly(p-phenylene), poly(triphenylene), polyazulene,polyfluorene, polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes).). In some embodiments, the resultingcathode or anode mixture has an electronic conductivity of at leastabout 10⁻⁶ S/cm. In other embodiments, the mixture has an electronicconductivity between approximately 10⁻⁶ S/cm and 10⁻³ S/cm. In otherembodiments, the mixture has an electronic conductivity of at leastabout 10⁻⁵ S/cm, or at least about 10⁻⁴ S/cm, of at least about 10⁻³S/cm, of at least about 10⁻² S/cm or more.

In some embodiments, the particles included in the semi-solid anode orcathode can be configured to have a partial or full conductive coating.

In some embodiments, the semi-solid ion-storing redox compositionincludes an ion-storing solid coated with a conductive coating material.In some embodiments, the conductive coating material has higher electronconductivity than the solid. In some embodiments, the solid is graphiteand the conductive coating material is a metal, metal carbide, metaloxide, metal nitride, or carbon. In some embodiments, the metal iscopper.

In some embodiments, the solid of the semi-solid ion-storing material iscoated with metal that is redox inert at the operating conditions of theredox energy storage device. In some embodiments, the solid of thesemi-solid ion storing material is coated with copper to increase theconductivity of the storage material particle, to increase the netconductivity of the semi-solid, and/or to facilitate charge transferbetween energy storage particles and conductive additives. In someembodiments, the storage material particle is coated with, about 1.5% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 3.0% by weight metallic copper. In someembodiments, the storage material particle is coated with about 8.5% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 10.0% by weight metallic copper. In someembodiments, the storage material particle is coated with about 15.0% byweight metallic copper. In some embodiments, the storage materialparticle is coated with about 20.0% by weight metallic copper.

In some embodiments, the conductive coating is placed on the cathode 140and/or anode 150 particles by chemical precipitation of the conductiveelement and subsequent drying and/or calcination.

In some embodiments, the conductive coating is placed on the cathode 140and/or anode 150 particles by electroplating (e.g., within a fluidizedbed).

In some embodiments, the conductive coating is placed on the cathode 140and/or anode 150 particles by co-sintering with a conductive compoundand subsequent comminution.

In some embodiments, the electrochemically active particles have acontinuous intraparticle conductive material or are embedded in aconductive matrix.

In some embodiments, a conductive coating and intraparticulateconductive network is produced by multicomponent-spray-drying, asemi-solid cathode 140 and/or anode 150 particles and conductivematerial particulates.

In some embodiments, the semi-solid composition also includes conductivepolymers that provide an electronically conductive element. In someembodiments, the conductive polymers are one or more of a polyacetylene,polyaniline, olythiophene, polypyrrole, poly(p-phenylene),poly(triphenylene), polyazulene, polyfluorene, polynaphtalene,polyanthracene, polyfuran, polycarbazole, polyacenes,poly(heteroacenes). In some embodiments, the conductive polymer is acompound that reacts in-situ to form a conductive polymer on the surfaceof the active material particles. In some embodiments, the compound canbe 2-hexylthiophene or 3-hexylthiophene and oxidizes during charging ofthe battery to form a conductive polymer coating on solid particles inthe cathode semi-solid suspension. In other embodiments, redox activematerial can be embedded in conductive matrix. The redox active materialcan coat the exterior and interior interfaces in a flocculated oragglomerated particulate of conductive material. In some embodiments,the redox-active material and the conductive material can be twocomponents of a composite particulate. Without being bound by any theoryor mode of operation, such coatings can pacify the redox activeparticles and can help prevent undesirable reactions with carrier liquidor electrolyte. As such, it can serve as a synthetic solid-electrolyteinterphase (SEI) layer.

In some embodiments, inexpensive iron compounds such as pyrite (FeS₂)are used as inherently electronically conductive ion storage compounds.In some embodiments, the ion that is stored is Li⁺.

In some embodiments, redox mediators are added to the semi-solid toimprove the rate of charge transfer within the semi-solid electrode. Insome embodiments, this redox mediator is ferrocene or aferrocene-containing polymer. In some embodiments, the redox mediator isone or more of tetrathiafulvalene-substituted polystyrene,ferrocene-substituted polyethylene, carbazole-substituted polyethylene.

In some embodiments, the surface conductivity or charge transferresistance of current collectors 110/120 used in the semi-solid batteryis increased by coating the current collector surface with a conductivematerial. Such layers can also serve as a synthetic SEI layer.Non-limiting examples of conductive coating materials include carbon, ametal, metal-carbide, metal nitride, metal oxide, or conductive polymer.In some embodiments, the conductive polymer includes but is not limitedto polyaniline or polyacetylene based conductive polymers orpoly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole, polythiophene,poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene,polynaphtalene, polyanthracene, polyfuran, polycarbazole,tetrathiafulvalene-substituted polystyrene, ferrocene-substitutedpolyethylene, carbazole-substituted polyethylene, polyoxyphenazine,polyacenes, or poly(heteroacenes). In some embodiments, the conductivepolymer is a compound that reacts in-situ to form a conductive polymeron the surface of the current collector. In some embodiments, thecompound is 2-hexylthiophene and oxidizes at a high potential to form aconductive polymer coating on the current collector. In someembodiments; the current collector is coated with metal that isredox-inert at the operating conditions of the redox energy storagedevice.

The semi-solid redox compositions can include various additives toimprove the performance of the redox cell. The liquid phase of thesemi-solids in such instances would comprise a solvent, in which isdissolved an electrolyte salt, and binders, thickeners, or otheradditives added to improve stability, reduce gas formation, improve SEIformation on the negative electrode particles, and the like. Examples ofsuch additives included vinylene carbonate (VC), vinylethylene carbonate(VEC), fluoroethylene carbonate (FEC), or alkyl cinnamates, to provide astable passivation layer on the anode or thin passivation layer on theoxide cathode, propane sultone (PS), propene sultone (PrS), or ethylenethiocarbonate as antigassing agents, biphenyl (BP), cyclohexylbenzene,or partially hydrogenated terphenyls, as gassing/safety/cathodepolymerization agents, or lithium bis(oxatlato)borate as an anodepassivation agent.

In some embodiments, the semi-solid cathode 140 and/or anode 150 caninclude a non-aqueous liquid electrolyte that can include polar solventssuch as, for example, alcohols or aprotic organic solvents. Numerousorganic solvents have been proposed as the components of Li-ion batteryelectrolytes, notably a family of cyclic carbonate esters such asethylene carbonate, propylene carbonate, butylene carbonate, and theirchlorinated or fluorinated derivatives, and a family of acyclic dialkylcarbonate esters, such as dimethyl carbonate, diethyl carbonate,ethylmethyl carbonate, dipropyl carbonate, methyl propyl carbonate,ethyl propyl carbonate, dibutyl carbonate, butylmethyl carbonate,butylethyl carbonate and butylpropyl carbonate. Other solvents proposedas components of Li-ion battery electrolyte solutions includey-butyrolactone, dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether,sulfolane, methylsulfolane, acetonitrile, propiononitrile, ethylacetate, methyl propionate, ethyl propionate, dimethyl carbonate,tetraglyme, and the like. These nonaqueous solvents are typically usedas multicomponent mixtures, into which a salt is dissolved to provideionic conductivity. Exemplary salts to provide lithium conductivityinclude LiClO₄, LiPF₆, LiBF₄, LiTFSI, LiBETI, LiBOB, and the like.

In some embodiments, the non-aqueous cathode 140 and/or anode 150semi-solid compositions are prevented from absorbing impurity water andgenerating acid (such as HF in the case of LiPF₆ salt) by incorporatingcompounds that getter water into the active material suspension, or intothe storage tanks or other plumbing of the system, for example, in thecase of redox flow cell batteries. Optionally, the additives are basicoxides that neutralize the acid. Such compounds include but are notlimited to silica gel, calcium sulfate (for example, the product knownas Drierite), aluminum oxide and aluminum hydroxide.

In some embodiment, the cathode 140 can be a semi-solid cathode and theanode 150 can be a conventional anode for example, a solid anode formedfrom the calendering process as is commonly known in the arts. In someembodiments, the cathode 140 can be a semi-solid cathode and the anode150 can also be a semi-solid anode as described herein. In someembodiments, the cathode 140 and the anode 150 can both be semi-solidflowable electrodes, for example, for use in a redox flow cell.

The following examples show the electrochemical properties of variouselectrochemical cells that include the semi-solid electrodes describedherein, compared with two conventional tablet batteries that includeLi-ion Tablet Battery 1 and Li-ion Tablet Battery 2. FIG. 2 summarizesthe electrochemical properties of the semi-solid electrode formulationsand the comparative batteries. These examples are only for illustrativepurposes and are not intended to limit the scope of the presentdisclosure.

COMPARATIVE EXAMPLE 1

A first commercially available tablet battery, Li-ion Tablet Battery 1(also referred to as “Comp Ex 1”) was discharged at various C-rates asshown in FIG. 2. At C/2 rate, corresponding to a current density ofabout 1 mA/cm², the Comp Ex 1 battery had an areal capacity of about 2.7mAh/cm². At 1 C rate, corresponding to a current density of about 2.2mA/cm², the areal capacity is still about 2.7 mAh/cm². However, abovecurrent density of about 5 mA/cm², the areal capacity drops rapidlyuntil it is nearly zero at about 10 mA/cm².

COMPARATIVE EXAMPLE 2

A second commercially available tablet battery, Li-ion Tablet Battery 2(also referred to as “Comp Ex 2”) was discharged at various C-rates asshown in FIG. 2. At C/2 rate, corresponding to a current density ofabout 1.75 mA/cm², the Comp Ex 1 battery had an areal capacity of about4.2 mAh/cm². At 1 C rate, corresponding to a current density of about 4mA/cm², the areal capacity is about 4 mAh/cm². However, above currentdensity of about 4 mA/cm², the areal capacity drops rapidly until it isnearly zero at about 7.5 mA/cm².

EXAMPLE 1

An electrochemical half cell Example 1 (also referred to as “Ex 1”) wasprepared using a semi-solid cathode and a Li metal anode. The LFPsemi-solid cathode was prepared by mixing 45 vol % LFP and 2 vol %carbon black with an ethylene carbonate/dimethyl carbonate/LiPF₆ basedelectrolyte. The cathode slurry was prepared using a batchmixer with aroller mill blade fitting. Mixing was performed at 100 rpm for 2minutes. The semi-solid slurry had a mixing index greater than 0.9 and aconductivity of 1.5×10⁻⁴ S/cm. The slurry was made into an electrode of250 μm thickness and was tested against a Li metal anode in a Swagelokcell configuration. The cell was tested using a Maccor battery testerand was cycled between a voltage range of V=2-4.2 V. The cell wascharged using a constant current-constant voltage with a constantcurrent rate at C/10 and C/8 for the first two cycles then at C/5 forthe latter cycles. The constant current charge is followed by a constantvoltage hold at 4.2 V until the charging current decreased to less thanC/20. The cell was discharged over a range of current densitiescorresponding to C-rates between C/10 and 5 C. FIG. 3A illustrates thecharge and discharge capacities as a function of the discharge C-ratefor the semi-solid electrode of Example 1, and FIG. 3B illustrates arepresentative charge and discharge curve at low C-rates. The nominalcell capacity of 2.23 mAh corresponds to complete utilization of the LFPcathode active material. As shown in FIG. 2, at C-rates below C/4, theEx 1 battery had an areal capacity greater than 7 mAh/cm², much greaterthan for the batteries in Comp Ex 1 and Comp Ex 2. At C/2 rate,corresponding to a current density of about 3.7 mA/cm², the Ex 1 batteryhad an areal capacity of about 6.8 mAh/cm². At 1 C rate, correspondingto a current density of about 6 mA/cm², the areal capacity is about 6mAh/cm². At these C-rates, the areal capacity is higher than for thebatteries in Comp Ex 1 and Comp Ex 2. Moreover, with increasing currentdensity beyond about 6 mA/cm², the areal capacity falls off much moregradually than for the batteries in Comp Ex 1 and Comp Ex 2.

EXAMPLE 2

An electrochemical half cell Example 2 (also referred to as “Ex 2”) wasprepared using a semi-solid cathode and a lithium metal anode. Thecathode slurry was prepared by mixing 45 vol % Li(Ni,Mn,Co)O₂ and 8 vol% carbon additive with an ethylene carbonate/dimethyl carbonate/LiPF₆based electrolyte. The cathode slurry was prepared using a batchmixerfitted with roller blades. Mixing was performed at 100 rpm for 4minutes. The cell was tested using a Maccor battery tester and wascycled over a voltage range of V=2-4.3 V. The cell was charged using aconstant current-constant voltage procedure with the constant currentportion being at C/10 and C/8 rate for the first two cycles then at C/5rate for later cycles. The constant current charge step was followed bya constant voltage hold at 4.2 V until the charging current decreased toless than C/20. The cell was then discharged over a range of currentdensity. As shown in FIG. 2, at C-rates below C/4, the Ex 2 battery hadan areal capacity greater than 10 mAh/cm², much greater than for thebatteries in Comp Ex 1 and Comp Ex 2. At C/2 rate, corresponding to acurrent density of about 4.5 mA/cm², the Ex 1 battery had an arealcapacity of about 9.5 mAh/cm². At 1 C rate, corresponding to a currentdensity of about 8 mA/cm², the areal capacity is about 8 mAh/cm². Atthese C-rates, the areal capacity is higher than for the batteries inComp Ex 1 and Comp Ex 2. Moreover, with increasing current densitybeyond about 6 mA/cm², the areal capacity falls off much more graduallythan for the batteries in Comp Ex 1 and Comp Ex 2.

EXAMPLE 3

An electrochemical full cell Example 3 (also referred to as “Ex 3”)included a semi-solid cathode formulated from 35 vol % Li(Ni,Mn,Co)O₂such that the semi-solid cathode had a thickness of 250 μm, and wastested against a semi-solid anode formulated from 40 vol % graphite and2 vol % carbon additive such that the anode had a thickness of 250 μm.The NMC semi-solid cathode was prepared by mixing 35 vol % NMC and 8 vol% carbon black with an ethylene carbonate/dimethyl carbonate/LiPF₆ basedelectrolyte. The cathode slurry was prepared using a batchmixer fittedwith roller blades. Mixing was performed at 100 rpm for 4 minutes. Thegraphite semi-solid anode was prepared by mixing 40 vol % graphite and 2vol % carbon black using the same electrolyte as the cathode. The anodeslurry formulation was mixed at 100 rpm for 30 seconds to yield asemi-solid anode suspension. The cathode and anode semi-solid slurrieswere formed into electrodes, each with 250 μm thickness. The electrodeswere used to form a NMC-Graphite based electrochemical full cell havingactive areas for both cathode and anode of approximately 80 cm². Theelectrochemical full cell Ex 3 was charged using a constantcurrent-constant voltage charging procedure (CC-CV) and a constantcurrent discharge between 2.75-4.2 V using a Maccor tester. The cell wasdischarged over a range of current densities. As shown in FIG. 2, atC-rates below C/4, the Ex 3 battery had an areal capacity of about 6mAh/cm², much greater than for the batteries in Comp Ex 1 and Comp Ex 2.At C/2 rate, corresponding to a current density of about 2.8 mA/cm², theEx 1 battery had an areal capacity of about 5.7 mAh/cm². At 1 C rate,corresponding to a current density of about 7.2 mA/cm², the arealcapacity is about 7.5 mAh/cm². At these C-rates, the areal capacity ishigher than for the batteries in Comp Ex 1 and Comp Ex 2. Moreover, withincreasing current density beyond about 6 mA/cm², the areal capacityfalls off much more gradually than for the batteries in Comp Ex 1 andComp Ex 2.

EXAMPLE 4

An electrochemical full cell Example 4 (also referred to as “Ex 4”)included a semi-solid cathode formulated from 35 vol % Li(Ni,Mn,Co)O₂such that the semi-solid cathode had a thickness of 500 μm, and wastested against a semi-solid anode formulated from 40 vol % graphite and2 vol % carbon additive such that the anode had a thickness of 500 μm.Both cathode and anode slurries and electrodes were prepared in asimilar manner to those in Ex. 3 except that the electrode thicknesseswere 500 μm. The Ex 4 electrochemical full cell has active areas forboth cathode and anode of approximately 80 cm². The Ex 4 full cell wascharged and discharge using a constant current-constant voltage chargingprocedure (CC-CV) and a constant current discharge between 2.75-4.2 Vusing a Maccor tester. The cell was discharged over a range of currentdensities. As shown in FIG. 2, at C-rates below C/4, the Ex 4 batteryreaches an areal capacity above 11 mAh/cm², much greater than for thebatteries in Comp Ex 1 and Comp Ex 2. At C/2 rate, corresponding to acurrent density of about 4.8 mA/cm², the Ex 1 battery had an arealcapacity of about 9.5 mAh/cm². At 1 C rate, corresponding to a currentdensity of about 6.8 mA/cm², the areal capacity is about 6.8 mAh/cm². Atthese C-rates, the areal capacity is higher than for the batteries inComp Ex 1 and Comp Ex 2. Moreover, with increasing current density, theareal capacity falls off much more gradually than for the batteries inComp Ex 1 and Comp Ex 2.

FIG. 2 shows that each of Ex 1, Ex 2, Ex 3 and Ex 4 have a substantiallysuperior areal capacity relative to Comp Ex 1 and Comp Ex 2 at C-ratesup to about 2 C. Furthermore, at very high C-rates, for example, C-ratesgreater than 2 C, these electrochemical cells that include semi-solidelectrodes still have an areal capacity superior to Comp Ex 1 and CompEx 2. For example, above about 10 mA/cm² current density, the arealcapacity of each of Comp Ex 1 and Comp Ex 2 is about 0 mAh/cm², whichmeans that no current can be drawn from the battery. In contrast, the Ex1, Ex 2, Ex 3 and Ex 4 cells still demonstrate a substantial arealcapacity at the 10 mA/cm² current density. Particularly the Ex 4 cellstill had about 5 mAh/cm² charge capacity at the 10 mA/cm² currentdensity corresponding to about 2 C rate, which is about 50% of the arealcapacity seen at the C/2 C-rate. Therefore, electrochemical cells thatinclude semi-solid electrodes described herein can have a higher arealcapacity than conventional electrochemical cells, and can also bedischarged at high C-rates while maintaining a significant percentage oftheir areal capacity.

While various embodiments of the system, methods and devices have beendescribed above, it should be understood that they have been presentedby way of example only, and not limitation. Where methods and stepsdescribed above indicate certain events occurring in certain order,those of ordinary skill in the art having the benefit of this disclosurewould recognize that the ordering of certain steps may be modified andsuch modification are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above. The embodiments have been particularlyshown and described, but it will be understood that various changes inform and details may be made.

1-28. (canceled)
 29. An electrochemical cell, comprising: an anode; asemi-solid cathode including a suspension of about 40% to about 75% byvolume of an active material and about 1% to about 6% by volume of aconductive material in a non-aqueous liquid electrolyte; and anion-permeable membrane disposed between the anode and the semi-solidcathode, wherein, the semi-solid cathode has a thickness in the range ofabout 250 μm to about 2,000 μm, and wherein the electrochemical cell hasan area specific capacity of at least 7 mAh/cm² at a C-rate of C/4. 30.The electrochemical cell of claim 29, wherein the semi-solid cathode hasan electronic conductivity of at least about 10⁻⁴ S/cm.
 31. Theelectrochemical cell of claim 29, wherein the semi-solid cathode has anarea specific capacity of at least 8 mAh/cm² at a C-rate of C/4.
 32. Theelectrochemical cell of claim 31, wherein the semi-solid cathode has anarea specific capacity of at least 9 mAh/cm² at a C-rate of C/4.
 33. Theelectrochemical cell of claim 32, wherein the semi-solid cathode has anarea specific capacity of at least 10 mAh/cm² at a C-rate of C/4. 34.The electrochemical cell of claim 29, wherein the active material in thesemi-solid cathode is about 50% to about 75% by volume.
 35. Theelectrochemical cell of claim 34, wherein the active material in thesemi-solid cathode is about 60% to about 75% by volume.
 36. Theelectrochemical cell of claim 29, wherein the semi-solid cathodesuspension has a mixing index of at least about 0.80.
 37. Theelectrochemical cell of claim 36, wherein the semi-solid cathodesuspension has a mixing index of at least about 0.90.
 38. Anelectrochemical cell, comprising: a semi-solid anode including asuspension of about 40% to about 75% by volume of a first activematerial and about 0% to about 10% by volume of a first conductivematerial in a first non-aqueous liquid electrolyte; a semi-solid cathodeincluding a suspension of about 40% to about 75% by volume of a secondactive material and about 1% to about 6% by volume of a secondconductive material in a second non-aqueous liquid electrolyte; and anion-permeable membrane disposed between the semi-solid anode and thesemi-solid cathode, wherein, the semi-solid anode and the semi-solidcathode each have a thickness in the range of about 250 μm to about2,000 μm, and wherein the electrochemical cell has an area specificcapacity of at least 7 mAh/cm² at a C-rate of C/4.
 39. Theelectrochemical cell of claim 38, wherein the semi-solid cathode has anarea specific capacity of at least 8 mAh/cm² at a C-rate of C/4.
 40. Theelectrochemical cell of claim 39, wherein the semi-solid cathode has anarea specific capacity of at least 9 mAh/cm² at a C-rate of C/4.
 41. Theelectrochemical cell of claim 40, wherein the semi-solid cathode has anarea specific capacity of at least 10 mAh/cm² at a C-rate of C/4. 42.The electrochemical cell of claim 38, wherein the first conductivematerial in the semi-solid anode is about 0.5% to about 2% by volume.43. The electrochemical cell of claim 38, wherein the second activematerial in the semi-solid cathode is about 50% to about 75% by volume.44. An electrochemical cell comprising: an anode; a semi-solid cathodeincluding a suspension of about 40% to about 75% by volume of an activematerial and about 1% to about 6% by volume of a conductive material ina non-aqueous liquid electrolyte; and an ion-permeable membrane disposedbetween the semi-solid anode and the semi-solid cathode, wherein, thesemi-solid cathode has a thickness in the range of about 250 μm to about2,000 μm, and wherein the electrochemical cell has an area specificcapacity of at least 7 mAh/cm² at a C-rate of C/2.
 45. Theelectrochemical cell of claim 44, wherein the semi-solid cathode has anarea specific capacity of at least 8 mAh/cm² at a C-rate of C/2.
 46. Theelectrochemical cell of claim 45, wherein the semi-solid cathode has anarea specific capacity of at least 9 mAh/cm² at a C-rate of C/2.
 47. Theelectrochemical cell of claim 46, wherein the semi-solid cathode has anarea specific capacity of at least 10 mAh/cm² at a C-rate of C/2. 48.The electrochemical cell of claim 44, wherein the semi-solid cathodesuspension has a mixing index of at least about 0.80.
 49. Theelectrochemical cell of claim 48, wherein the semi-solid cathodesuspension has a mixing index of at least about 0.90.
 50. Anelectrochemical cell, comprising: a semi-solid anode including asuspension of about 40% to about 75% by volume of a first activematerial and about 0% to about 10% by volume of a first conductivematerial in a first non-aqueous liquid electrolyte; a semi-solid cathodeincluding a suspension of about 40% to about 75% by volume of a secondactive material and about 1% to about 6% by volume of a secondconductive material in a second non-aqueous liquid electrolyte; and anion-permeable membrane disposed between the semi-solid anode and thesemi-solid cathode, wherein, the semi-solid anode and the semi-solidcathode each have a thickness in the range of about 250 μm to about2,000 μm, and wherein the electrochemical cell has an area specificcapacity of at least 7 mAh/cm² at a C-rate of C/2.
 51. Theelectrochemical cell of claim 50, wherein the electrochemical cell hasan area specific capacity of at least 7 mAh/cm² at a C-rate of C/4. 52.The electrochemical cell of claim 51, wherein the electrochemical cellhas an area specific capacity of at least 8 mAh/cm² at a C-rate of C/4.53. The electrochemical cell of claim 50, wherein the semi-solid anodeand the semi-solid cathode each have a thickness in the range of about250 μm to about 600 μm.
 54. The electrochemical cell of claim 53,wherein the semi-solid anode and the semi-solid cathode each have athickness in the range of about 300 μm to about 600 μm.
 55. Theelectrochemical cell of claim 54, wherein the semi-solid anode and thesemi-solid cathode each have a thickness in the range of about 350 μm toabout 600 μm.
 56. The electrochemical cell of claim 55, wherein thesemi-solid anode and the semi-solid cathode each have a thickness in therange of about 400 μm to about 600 μm.
 57. The electrochemical cell ofclaim 50, wherein the first conductive material in the semi-solid anodeis about 0.5% to about 2% by volume.
 58. The electrochemical cell ofclaim 50, wherein the second active material in the semi-solid cathodeis about 50% to about 75% by volume.